This is certainly strange. We are not aware of any known issues around compatibility of Roslyn with Code Contracts.

From the exception message above looks like you probably have a localized (German?) OS. An online translator tells me that the exception message "Gltiges TypeDef oder TypeRef-Token nach ELEMENT_TYPE_GENERICINST erwartet." translates to "TypeDef
or TypeRef token is expected to/after ELEMENT_TYPE_GENERICINST". I am not sure exactly what this means / how this may have been caused by Roslyn.

Its good to know that reinstalling Roslyn and Code Contracts fixed the issue. But do you have any additional details that may help us figure out what may have caused this? Thanks!